Method and apparatus for transmitting control information

ABSTRACT

The present invention relates to a wireless communication system. More particularly, the present invention relates to a method and apparatus for transmitting uplink control information in the event that a plurality of cells is constructed, wherein the method comprises the following steps: receiving a PDCCH and/or a PDSCH; generating acknowledgement information on the PDCCH and/or PDSCH; and, if acknowledgement information transmission timing and channel state information transmission timing collide with each other, dropping the channel state information and transmitting only the acknowledgement information, or transmitting the acknowledgement information and the channel state information together in accordance with a predetermined condition.

TECHNICAL FIELD

The present invention relates to a wireless communication system, andmore particularly, to a method and apparatus for transmitting controlinformation.

BACKGROUND ART

Wireless communication systems have been widely deployed to providevarious types of communication services including voice and dataservices. In general, a wireless communication system is a multipleaccess system that supports communication of multiple users by sharingavailable system resources (e.g. a bandwidth, transmission power, etc.)among the multiple users. The multiple access system may adopt amultiple access scheme such as Code Division Multiple Access (CDMA),Frequency Division Multiple Access (FDMA), Time Division Multiple Access(TDMA), Orthogonal Frequency Division Multiple Access (OFDMA), or SingleCarrier Frequency Division Multiple Access (SC-FDMA).

DISCLOSURE Technical Problem

An object of the present invention is to provide a method and apparatusfor efficiently transmitting control information in a wirelesscommunication system.

Another object of the present invention is to provide a method andapparatus for efficiently transmitting multiple uplink controlinformation and efficiently managing resources for the uplink controlinformation transmission when the multiple uplink control informationneed to be transmitted in the same subframe.

It will be appreciated by persons skilled in the art that the objectsthat could be achieved with the present invention are not limited towhat has been particularly described hereinabove and the above and otherobjects that the present invention could achieve will be more clearlyunderstood from the following detailed description taken in conjunctionwith the accompanying drawings.

Technical Solution

According to an aspect of the present invention, the objects of thepresent invention can be achieved by providing a method of transmittinguplink control information at a communication apparatus in a timedivision duplex (TDD) wireless communication system, the methodcomprising: receiving at least one of one or more physical downlinkcontrol channels (PDCCHs) and one or more physical downlink sharedchannels (PDCCHs); and generating reception response information aboutthe at least one of the one or more PDCCHs and the one or more PDCCHs,wherein when a transmission time of the reception response informationand a transmission time of channel status information collide, if acertain condition is satisfied, the reception response information andthe channel status information are transmitted together using a firstphysical uplink control channel (PUCCH) format, wherein when thetransmission time of the reception response information and thetransmission time of the channel status information collide, if thecertain condition is not satisfied, the reception response informationis transmitted using a second PUCCH format and the channel statusinformation is dropped, wherein the certain condition includes at leastone of the following conditions (1) to (3):

-   -   (1) a single PDSCH transmission only on a primary cell (PCell)        indicated by detection of a PDCCH having a downlink assignment        index (DAI) initial value is present;    -   (2) a single PDCCH transmission only on the PCell that has the        DAI initial value and indicates a semi-persistent scheduling        (SPS) release is present; and    -   (3) a single PDSCH transmission only on the PCell where there is        not a corresponding PDCCH is present.

According to another aspect of the present invention, the objects of thepresent invention can be achieved by providing a communication apparatusconfigured to transmit uplink control information in a Time DivisionDuplex (TDD) wireless communication system, the communication apparatuscomprising: a Radio Frequency (RF) unit; and a processor configured toreceive at least one of one or more Physical Downlink Control CHannels(PDCCHs) and one or more Physical Downlink Shared CHannels (PDSCHs), andto generate reception response information about the at least one of theone or more PDCCHs and the one or more PDSCHs, wherein when atransmission time of the reception response information and atransmission time of channel status information collide, if a certaincondition is satisfied, the reception response information and thechannel status information are transmitted together using a firstPhysical Uplink Control CHannel (PUCCH) format, wherein when thetransmission time of the reception response information and thetransmission time of the channel status information collide, if thecertain condition is not satisfied, the reception response informationis transmitted using a second PUCCH format and the channel statusinformation is dropped, wherein the certain condition includes at leastone of the following conditions (1) to (3):

(1) a single PDSCH transmission only on a Primary Cell (PCell) indicatedby detection of a PDCCH having a Downlink Assignment Index (DAI) initialvalue is present;

(2) a single PDCCH transmission only on the PCell that has the DAIinitial value and indicates a Semi-Persistent Scheduling (SPS) releaseis present; and

(3) a single PDSCH transmission only on the PCell where there is not acorresponding PDCCH is present.

If the certain condition is not satisfied, resource for the second PUCCHformat may be indicated by a value of Transmit Power Control (TPC) fieldof one or more Secondary Cell (SCell) PDCCH and/or one or more PCellPDCCH not corresponding to the DAI initial value.

The at least one of one or more PDCCHs and one or more PDSCHs may bereceived in a subframe n−k (kεK), the reception response information maybe transmitted in a subframe n, and K may be given by the below table inaccordance with UL-DL configuration.

UL-DL Configu- Subframe n ration 0 1 2 3 4 5 6 7 8 9 0 — — 6 — 4 — — 6 —4 1 — — 7, 6 4 — — — 7, 6 4 — 2 — — 8, 7, 4, 6 — — — — 8, 7, — — 4, 6 3— — 7, 6, 11 6, 5 5, 4 — — — — — 4 — — 12, 8, 7, 6, 5, — — — — — — 11 4,7 5 — — 13, 12, 9, — — — — — — — 8, 7, 5, 4, 11, 6 6 — — 7 7 5 — — 7 7 —

The DAI initial value may be 1.

The first PUCCH format may be a PUCCH format 2, 2a or 2b.

The second PUCCH format may be a PUCCH format 3.

Advantageous Effects

According to embodiments of the present invention, it is possible toefficiently transmit control information in a wireless communicationsystem. Specifically, when multiple pieces of uplink control informationneed to be transmitted in the same subframe, the uplink controlinformation can be efficiently transmitted and resources for the uplinkcontrol information transmission can be efficiently managed.

It will be appreciated by persons skilled in the art that that theeffects that could be achieved with the present invention are notlimited to what has been particularly described hereinabove and otheradvantages of the present invention will be more clearly understood fromthe following detailed description taken in conjunction with theaccompanying drawings.

DESCRIPTION OF DRAWINGS

The accompanying drawings, which are included to provide a furtherunderstanding of the invention, illustrate embodiments of the inventionand together with the description serve to explain the principle of theinvention.

In the drawings:

FIG. 1 illustrates physical channels and signal transmission on thephysical channels in a 3GPP LTE system;

FIG. 2A illustrates an exemplary radio frame structure;

FIG. 2B illustrates an exemplary resource grid of a downlink slot;

FIG. 3 illustrates an exemplary downlink subframe structure;

FIG. 4 illustrates an exemplary uplink subframe structure;

FIG. 5 illustrates an example of physically mapping a PUCCH format to aPUCCH region;

FIG. 6 illustrates a slot level structure of PUCCH format 2/2a/2b;

FIGS. 7 and 8 illustrate a method of multiplexing ACK/NACK (A/N) and CSIat a user equipment (UE);

FIG. 9 illustrates a slot level structure of PUCCH format 1a/1b;

FIG. 10 illustrates an example of determining a PUCCH resource forACK/NACK;

FIG. 11 illustrates a carrier aggregation (CA) communication system;

FIG. 11 illustrates cross-carrier scheduling;

FIG. 12 illustrates cross-carrier scheduling;

FIGS. 13 and 14 illustrate a block-spreading based E-PUCCH format;

FIG. 15 illustrates an example of dropping CSI when an ACK/NACKtransmission time and a CSI transmission time collide;

FIG. 16 illustrates an example of transmitting ACK/NACK and an SRtogether;

FIG. 17 illustrates a UCI transmission scheme according to an embodimentof the present invention;

FIG. 18 illustrates a UCI transmission scheme according to anotherembodiment of the present invention; and

FIG. 19 illustrates a base station (BS) and a UE to which embodiments ofthe present invention can be applied.

BEST MODE

Embodiments of the present invention are applicable to a variety ofwireless access technologies such as Code Division Multiple Access(CDMA), Frequency Division Multiple Access (FDMA), Time DivisionMultiple Access (TDMA), Orthogonal Frequency Division Multiple Access(OFDMA), and Single Carrier Frequency Division Multiple Access(SC-FDMA). CDMA can be implemented as a radio technology such asUniversal Terrestrial Radio Access (UTRA) or CDMA2000. TDMA can beimplemented as a radio technology such as Global System for Mobilecommunications (GSM)/General Packet Radio Service (GPRS)/Enhanced DataRates for GSM Evolution (EDGE). OFDMA can be implemented as a radiotechnology such as Institute of Electrical and Electronics Engineers(IEEE) 802.11 (Wireless Fidelity (Wi-Fi)), IEEE 802.16 (Worldwideinteroperability for Microwave Access (WiMAX)), IEEE 802.20, EvolvedUTRA (E-UTRA). UTRA is a part of Universal Mobile TelecommunicationsSystem (UMTS). 3^(rd) Generation Partnership Project (3GPP) Long TermEvolution (LTE) is a part of Evolved UMTS (E-UMTS) using E-UTRA,employing OFDMA for downlink and SC-FDMA for uplink. LTE-Advanced(LTE-A) is an evolution of 3GPP LTE.

While the following description is given, centering on 3GPP LTE/LTE-A toclarify the description, this is purely exemplary and thus should not beconstrued as limiting the present invention.

In a wireless communication system, a user equipment (UE) receivesinformation from a base station (BS) through a downlink (DL) andtransmits information to the BS through an uplink (UL). Informationtransmitted/received between the UE and the BS includes data and controlinformation, and various physical channels exist according totype/purpose of the information.

FIG. 1 illustrates physical channels and signal transmission on thephysical channels in a 3GPP LTE system.

Referring to FIG. 1, when a UE is powered on or enters a new cell, theUE performs an initial cell search involving acquisition ofsynchronization with a BS in step S101. For the initial cell search, theUE receives a Primary Synchronization CHannel (P-SCH) and a SecondarySynchronization CHannel (S-SCH) from the BS, and acquiressynchronization with the BS and information such as a cell Identity (ID)from the P-SCH and the S-SCH. Then the UE may receive a PhysicalBroadcast CHannel (PBCH) from the BS and acquire broadcast informationwithin a cell from the PBCH. The UE may check a downlink channel stateby receiving a downlink reference signal (DL RS) in the initial cellsearch step.

Upon completion of the initial cell search, the UE may acquire morespecific system information by receiving a Physical Downlink ControlCHannel (PDCCH) and receiving a Physical Downlink Shared CHannel (PDSCH)according to information carried on the PDCCH in step S102.

Subsequently, the UE may perform a random access procedure (S103 toS106) in order to complete access to the BS. For the random accessprocedure, the UE may transmit a preamble on a Physical Random AccessCHannel (PRACH) (S103) and receive a response message to the preamble ona PDSCH (S104). If the random access procedure is contention-based, theUE may additionally perform a contention resolution procedure such astransmission of an additional PRACH (S105) and reception of a PDCCH anda PDSCH corresponding to the PDCCH (S106).

After the above random access procedure, the UE may receive aPDCCH/PDSCH (S107) and transmit a Physical Uplink Shared CHannel(PUSCH)/Physical Uplink Control CHannel (PUCCH) (S108) in a generaluplink/downlink signal transmission procedure. Control information thatthe UE transmits to the BS is referred to as uplink control information(UCI). The UCI includes a Hybrid Automatic Repeat and reQuestACKnowledgment/Negative-ACK (HARQ ACK/NACK) signal, a Scheduling Request(SR), Channel Quality Indictor (CQI), a Precoding Matrix Index (PMI),and a Rank Indicator (RI). In the specification, the HARQ ACK/NACK issimply referred to as a HARQ-ACK or ACK/NACK (A/N). The HARQ-ACKincludes at least one of a positive ACK (simply, ACK), a negative ACK(NACK), DTX and NACK/DTX. The UCI is transmitted on a PUCCH, in general.However, the UCI can be transmitted on a PUSCH when control informationand traffic data need to be transmitted simultaneously. Furthermore, theUCI can be non-periodically transmitted on a PUSCH at therequest/instruction of a network.

FIG. 2A illustrates a radio frame structure. In a cellular OFDM wirelesspacket communication system, UL/DL data packet transmission is performedbased on subframe. One subframe is defined as a predetermined intervalincluding a plurality of OFDM symbols. 3GPP LTE standard supports type-1radio frame applicable to Frequency Division Duplex (FDD) and type-2radio frame applicable to Time Division Duplex (TDD).

FIG. 2A (a) illustrates a type-1 radio frame structure. A DL radio frameincludes 10 subframes each having 2 slots in the time domain. A timerequired to transit one subframe is referred to as Transmission TimeInterval (TTI). For example, one subframe is 1 ms long and one slot is0.5 ms long. One slot includes a plurality of OFDM symbols in the timedomain and a plurality of Resource Blocks (RBs) in the frequency domain.Since 3GPP LTE systems use OFDMA on a downlink, an OFDM symbolrepresents one symbol interval. The OFDM symbol can be called a SC-FDMAsymbol or symbol interval. A RB as a resource allocation unit mayinclude a plurality of consecutive subcarriers in one slot.

The number of OFDM symbols included in one slot may depend on CyclicPrefix (CP) configuration. CPs include an extended CP and a normal CP.When an OFDM symbol is configured with the normal CP, for example, thenumber of OFDM symbols included in one slot may be 7. When an OFDMsymbol is configured with the extended CP, the length of one OFDM symbolincreases, and thus the number of OFDM symbols included in one slot issmaller than that in case of the normal CP. In case of the extended CP,the number of OFDM symbols allocated to one slot may be 6. When achannel state is unstable, such as a case in which a UE moves at a highspeed, the extended CP can be used to reduce inter-symbol interference.

When the normal CP is used, one subframe includes 14 OFDM symbols sinceone slot has 7 OFDM symbols. The first three OFDM symbols at most ineach subframe can be allocated to a PDCCH and the remaining OFDM symbolscan be allocated to a PDSCH.

FIG. 2A (b) illustrates a type-2 radio frame structure. The type-2 radioframe includes 2 half frames. Each half frame includes 5 subframes, aDownlink Pilot Time Slot (DwPTS), a Guard Period (GP), and an UplinkPilot Time Slot (UpPTS), and one subframe consists of 2 slots. The DwPTSis used for initial cell search, synchronization or channel estimation.The UpPTS is used for channel estimation in a BS and UL transmissionsynchronization acquisition in a UE. The GP eliminates UL interferencecaused by multi-path delay of a DL signal between a UL and a DL.

The radio frame structure is merely exemplary and the number ofsubframes included in the radio frame, the number of slots included in asubframe, and the number of symbols included in a slot can be vary.

FIG. 2B illustrates a resource grid of a DL slot.

Referring to FIG. 2B, a DL slot includes a plurality of OFDM symbols inthe time domain. One DL slot may include 7 (6) OFDM symbols, and aResource Block (RB) may include 12 subcarriers in the frequency domain.Each element on the resource grid is referred to as a Resource Element(RE). One RB includes 12×7 (6) REs. The number of RBs in a DL slot,N_(RB), depends on a DL transmission band. A UL slot has the samestructure as the DL slot and includes SC-FDMA symbols instead of OFDMsymbols.

FIG. 3 illustrates a downlink subframe structure.

Referring to FIG. 3, the first three or four OFDM symbols in the firstslot of a subframe correspond to a control region to which a controlchannel is allocated and the remaining OFDM symbols correspond to a dataregion to which a PDSCH is allocated. Examples of a DL control channelused in an LTE system include a Physical Control Format IndicatorCHannel (PCFICH), a Physical Downlink Control Channel (PDCCH), aPhysical Hybrid ARQ Indicator Channel (PHICH), etc. The PCFICH istransmitted through the first OFDM symbol of a subframe and carriesinformation on the number of OFDM symbols used for control channeltransmission in the subframe. The PHICH carries a Hybrid AutomaticRepeat reQuest ACK/NACK (HARQ ACK/NACK) signal in response to uplinktransmission.

Control information transmitted on the PDCCH is referred to as DownlinkControl Information (DCI). The DCI includes resource allocationinformation and control information for a UE or a UE group. For example,the DCI includes UL/DL scheduling information, a UL transmission (Tx)power control command, etc.

The PDCCH carries transport format and resource allocation informationof a Downlink Shared CHannel (DL-SCH), transport format and resourceallocation information of an Uplink Shared Channel (UL-SCH), paginginformation on a Paging CHannel (PCH), system information on the DL-SCH,resource allocation information of a higher-layer control message, suchas a random access response transmitted on a PDCCH, a Tx power controlcommand set with respect to individual UEs in a UE group, a Tx powercontrol command, enabling information of Voice over IP (VoIP), etc. Aplurality of PDCCHs can be transmitted in the control region. A UE canmonitor the plurality of PDCCHs. The PDCCH is transmitted on aggregationof one or more consecutive Control Channel Elements (CCEs). A CCE is alogical allocation unit used to provide a coding rate based on a radiochannel state to the PDCCH. The CCE corresponds to a plurality ofResource Element Groups (REGs). The format of the PDCCH and the numberof bits of the PDCCH are determined on the basis of the number of CCEs.A BS determines a PDCCH format according to DCI to be transmitted to aUE and adds Cyclic Redundancy Check (CRC) to control information. TheCRC is masked by an identifier (e.g. Radio Network Temporary Identifier(RNTI)) according to the owner or purpose of the PDCCH. For example,when the PDCCH is destined for a specific UE, the CRC can be masked bythe identifier (e.g. cell-RNTI (C-RNTI)) of the specific UE. When thePDCCH is for a paging message, the CRC can be masked by a pagingidentifier (e.g. paging-RNTI (P-RNTI)). When the PDCCH is for systeminformation (more specifically, a System Information Block (SIC)), theCRC can be masked by a System Information RNTI (SI-RNTI). When the PDCCHis for a random access response, the CRC can be masked by a RandomAccess RNTI (RA-RNTI).

FIG. 4 illustrates an uplink subframe structure used in an LTE system.

Referring to FIG. 4, an uplink subframe includes a plurality of slots(e.g. two slots). The slots may include different numbers of SC-FDMAsymbols according to CP length. The uplink subframe is divided into adata region and a control region in the frequency domain. The dataregion includes a PUSCH and is used to transmit a data signal such asaudio data. The control region includes a PUCCH and is used to transmitUCI. The PUCCH includes RB pairs located on both ends of the data regionin the frequency domain and is hopped based on slots.

The PUCCH can be used to transmit the following control information.

-   -   Scheduling Request (SR): This is information used to request a        UL-SCH resource and is transmitted using On-Off Keying (OOK)        scheme.    -   HARQ ACK/NACK: This is a response signal to a downlink data        packet on a PDSCH and indicates whether the downlink data packet        has been successfully received. A 1-bit ACK/NACK signal is        transmitted as a response to a single downlink codeword and a        2-bit ACK/NACK signal is transmitted as a response to two        downlink codewords.    -   Channel Quality Indicator (CQI): This is feedback information        about a downlink channel. Feedback information regarding        Multiple Input Multiple Output (MIMO) includes Rank Indicator        (RI), Precoding Matrix Indicator (PMI), Precoding Type Indicator        (PTI), etc. 20 bits are used for each subframe.

The quantity of control information (UCI) that a UE can transmit througha subframe depends on the number of SC-FDMA symbols available forcontrol information transmission. The SC-FDMA symbols available forcontrol information transmission correspond to SC-FDMA symbols otherthan SC-FDMA symbols of the subframe, which are used for referencesignal transmission. In the case of a subframe in which a SoundingReference Signal (SRS) is configured, the last SC-FDMA symbol of thesubframe is excluded from the SC-FDMA symbols available for controlinformation transmission. A reference signal is used to detect coherenceof the PUCCH. The PUCCH supports 7 formats according to informationtransmitted thereon.

Table 1 shows the mapping relationship between PUCCH formats and UCI inan LTE system.

TABLE 1 PUCCH format UCI (Uplink Control Information) Format 1 SR(Scheduling Request) (non-modulated waveform Format 1a 1-bit HARQACK/NACK (SR exist/non-exist) Format 1b 2-bit HARQ ACK/NACK (SRexist/non-exist) Format 2 CQI (20 coded bits) Format 2 CQI and 1- or2-bit HARQ ACK/NACK (20 bits) (corresponding to only extended CP) Format2a CQI and 1-bit HARQ ACK/NACK (20 + 1 coded bits) Format 2b CQI and2-bit HARQ ACK/NACK (20 + 2 coded bits)

An SRS is transmitted through the last symbol in one subframe in thetime domain. SRSs of multiple UEs, which are transmitted through thelast symbol of the same subframe, can be identified according tofrequency position/sequence. In LTE, an SRS is periodically transmitted.Configuration for periodic SRS transmission is achieved by acell-specific SRS parameter and a UE-specific SRS parameter. Thecell-specific SRS parameter (in other words, cell-specific SRSconfiguration) and the UE-specific SRS parameter (in other words,UE-specific SRS configuration) are transmitted to a UE through higherlayer (e.g. RRC) signaling.

The cell-specific SRS parameter includes srs-BandwidthConfig andsrs-SubframeConfig. Here, srs-BandwidthConfig indicates informationabout a frequency bandwidth in which an SRS can be transmitted in a celland srs-SubframeConfig indicates information about a subframe in whichthe SRS can be transmitted in the cell. The subframe in which the SRScan be transmitted in the cell is periodically set. The UE-specific SRSparameter includes srs-Bandwidth, srs-HoppingBandwidth,freqDomainPosition, srs-ConfigIndex, transmissionComb and cyclicShift.Here, srs-Bandwidth represents a value used to set a frequency bandwidthin which the corresponding UE transmits the SRS and srs-HoppingBandwidthindicates a value used to set frequency hopping of the SRS.FreqDomainPosition represents a value used to determine a frequencyposition in which the SRS is transmitted and srs-ConfigIndex indicates avalue used to set a subframe in which the corresponding UE transmits theSRS. In addition, transmissionComb denotes a value used to set SRStransmission comb and cyclicShift represents a value used to set acyclic shift value applied to an SRS sequence.

FIG. 5 illustrates an example of physically mapping a PUCCH format to aPUCCH region.

Referring to FIG. 5, PUCCH formats are mapped onto RBs in the order ofPUCCH formats 2/2a/2b (CQI) (e.g. PUCCH regions m=0, 1), PUCCH formats2/2a/2b (CQI) or PUCCH formats 1/1a/1b (SR/HARQ ACK/NACK) (e.g. PUCCHregion m=2 if present), and PUCCH formats 1/1a/1b (SR/HARQ ACK/NACK)(e.g. PUCCH regions m=3, 4, 5), starting from the band-edge, andtransmitted. The number of PUCCH RBs, N_(RB) ⁽²⁾, which can be used forPUCCH formats 2/2a/2b (CQI) is signaled to a UE in a cell throughbroadcast signaling.

FIG. 6 illustrates a slot level structure of PUCCH formats 2/2a/2b. ThePUCCH formats 2/2a/2b are used for CSI transmission. CSI includes CQI,PMI, RI, etc. In the case of normal CP, SC-FDMA symbols #1 and #5 in aslot are used for transmission of a Demodulation Reference Signal (DMRS). In the case of extended CP, only SC-FDMA #3 in the slot is used forDM RS transmission.

Referring to FIG. 6, at a subframe level, 10-bit CSI is channel-codedinto 20 coded bits using (20, k) Reed-Muller code punctured at a rate of½ (not shown). The coded bits are scrambled (not shown) and then mappedto Quadrature Phase Shift Keying (QPSK) constellation (QPSK modulation).Scrambling can be performed using length-31 gold sequence in a similarmanner that PUSCH data is scrambled. 10 QPSK modulation symbols aregenerated according to the QPSK modulation, and 5 QPSK modulationsymbols d₀, d₁, d₂, d₃ and d₄ are transmitted through SC-FDMA symbolscorresponding thereto in each slot. Each of the QPSK modulation symbolsis used to modulate a length-12 base RS sequence r_(u,0) prior to beingsubjected to Inverse Fast Fourier Transform (IFFT). Consequently, the RSsequence is cyclic-shifted in the time domain according to the QPSKmodulation symbol value (d_(x)*r_(u,0) ^((αx)), x=0 to 4). The RSsequence multiplied by the QPSK modulation symbol is cyclic-shifted(α_(cs,x), x=1,5). When the number of cyclic shifts is N, N UEs can bemultiplexed on the same CSI PUCCH RB. While a DM RS sequence is similarto a CSI sequence in the frequency domain, the DM RS sequence is notmodulated by a CSI modulation symbol.

Parameters/resources for periodic CSI reports are configuredsemi-statically according to higher layer (e.g. Radio Resource Control(RRC) signaling. If PUCCH resource index n_(PUCCH) ⁽²⁾ is set for CSItransmission, for example, CSI is periodically transmitted on a CSIPUCCH linked to PUCCH resource index n_(PUCCH) ⁽²⁾. PUCCH resource indexn_(PUCCH) ⁽²⁾ indicates a PUCCH RB and cyclic shift α_(cs).

FIGS. 7 and 8 illustrate a method of multiplexing ACK/NACK and CSI at aUE.

In LTE, simultaneous transmission of ACK/NACK and CSI according to theUE is enabled by UE-specific higher layer signaling. When simultaneoustransmission is not enabled and ACK/NACK needs to be transmitted on aPUCCH in a subframe to which CSI report is set, the CSI is dropped andonly ACK/NACK is transmitted using PUCCH format 1a/1b. In the case of asubframe permitted by a BS to be used for the UE to simultaneouslytransmit ACK/NACK and CSI, the CSI and 1-bit or 2-bit ACK/NACK aremultiplexed to the same PUCCH RB. This method is implemented differentlyin normal CP case and in extended CP case.

In case of normal CP, to simultaneously transmit 1-bit or 2-bit ACK/NACKand CSI (format 2a/2b), the UE modulates (unscrambled) ACK/NACK bits, asshown in FIG. 7. Accordingly, one ACK/NACK modulated symbol d_(HARQ).ACK is coded into a binary value ‘1’ and NACK is coded into a binaryvalue ‘0’. The single ACK/NACK modulated symbol d_(HARQ) is used formodulation of the second RS (i.e. SC-FDMA symbol #5) in each slot. Thatis, ACK/NACK is signaled using an RS for PUCCH format 2a/2b. The CSI isloaded in a UCI data part of PUCCH format 2a/2b. FIG. 7 illustrates thatNACK (or NACK and NACK in case of two MIMO codewords) ismodulation-mapped to +1 (no RS modulation). DTX (DiscontinuousTransmission) is processed into NACK. DTX represents that the UE failsto detect a DL grant PDCCH.

In case of extended CP (one symbol per slot), 1-bit or 2-bit HARQACK/NACK and CSI are joint-coded to generate a (20, k_(CSI)+k_(A/N))Reed-Muller based block code. A 20-bit codeword is transmitted on aPUCCH using the CSI channel structure shown in FIG. 6. Joint coding ofACK/NACK and CSI is performed as illustrated in FIG. 8. A maximum of thenumber of information bits supported by a block code is 13. In case oftransmission of two codewords in downlink, k_(CSI)=11 CSI bits andk_(A/N)=2 bits.

FIG. 9 illustrates a slot level structure of PUCCH formats 1a/1b. ThePUCCH formats 1a/1b are used for ACK/NACK transmission. In the case ofnormal CP, SC-FDMA symbols #2, #3 and #4 are used for DM RStransmission. In the case of extended CP, SC-FDMA symbols #2 and #3 areused for DM RS transmission. Accordingly, 4 SC-FDMA symbols in a slotare used for ACK/NACK transmission.

Referring to FIG. 9, 1-bit and 2-bit ACK/NACK information are modulatedaccording to BPSK and QPSK modulation schemes respectively, to generateone ACK/NACK modulation symbol d₀. The ACK/NACK information correspondsto 1 in the case of positive ACK and corresponds to 0 in case ofnegative ACK (NACK). Table 2 shows a modulation table defined for PUCCHformats 1a and 1b in a conventional LTE system.

TABLE 2 PUCCH format b(0), . . . , b(M_(bit) − 1) d(0) 1a 0 1 1 −1   1b00 1 01 −j 10 j 11 −1  

PUCCH formats 1a/1b perform time domain spreading using an orthogonalspreading code W₀, W₁, W₂, W₃, (e.g. Walsh-Hadamard or DFT code) inaddition to cyclic shift α_(cs,x) in the frequency domain. In the caseof PUCCH formats 1a/1b, a larger number of UEs can be multiplexed on thesame PUCCH RB because code multiplexing is used in both frequency andtime domains.

RSs transmitted from different UEs are multiplexed using the same methodas used to multiplex UCI. The number of cyclic shifts supported bySC-FDMA symbols for PUCCH ACK/NACK RB can be configured by cell-specifichigher layer signaling parameter Δ_(shift) ^(PUCCH). Δ_(shift)^(PUCCH)ε{1, 2, 3} represents that shift values are 12, 6 and 4,respectively. In time-domain CDM, the number of spreading codes actuallyused for ACK/NACK can be limited by the number of RS symbols becausemultiplexing capacity of RS symbols is less than that of UCI symbols dueto a smaller number of RS symbols.

FIG. 10 illustrates an example of determining PUCCH resources forACK/NACK. In an LTE system, a plurality of PUCCH resources for ACK/NACKare shared by a plurality of UEs in a cell every time the UEs need thePUCCH resources rather than allocated to UEs in advance. Specifically, aPUCCH resource used by a UE to transmit an ACK/NACK signal correspondsto a PDCCH on which scheduling information on DL data involving theACK/NACK signal is delivered. The region in which the PDCCH istransmitted in a DL subframe is configured with a plurality of ControlChannel Elements (CCEs), and the PDCCH transmitted to the UE is composedof one or more CCEs. The UE transmits the ACK/NACK signal through aPUCCH resource corresponding to a specific one (e.g. first CCE) of theCCEs constituting the received PDCCH.

Referring to FIG. 10, each block in a Downlink Component Carrier (DL CC)represents a CCE and each block in an Uplink Component Carrier (UL CC)indicates a PUCCH resource. Each PUCCH index corresponds to a PUCCHresource for an ACK/NACK signal. If information on a PDSCH is deliveredon a PDCCH composed of CCEs #4, #5 and #6, as shown in FIG. 8, a UEtransmits an ACK/NACK signal on PUCCH #4 corresponding to CCE #4, thefirst CCE of the PDCCH. FIG. 8 illustrates a case in which maximum MPUCCHs are present in the UL CC when maximum N CCEs exist in the DL CC.Though N can equal M, N may differ from M and CCEs are mapped to PUCCHsin an overlapped manner.

Specifically, a PUCCH resource index in an LTE system is determined asfollows.

n ⁽¹⁾ _(PUCCH) =n _(CCE) +N ⁽¹⁾ _(PUCCH)  [Equation 1]

Here, n⁽¹⁾ _(PUCCH) represents a resource index of PUCCH format 1 forACK/NACK/DTX transmission, N⁽¹⁾ _(PUCCH) denotes a signaling valuereceived from a higher layer, and n_(CCE) denotes the smallest value ofCCE indexes used for PDCCH transmission. A cyclic shift, an orthogonalspreading code and a Physical Resource Block (PRB) for PUCCH formats1a/1b are obtained from n⁽¹⁾ _(PUCCH).

When the LTE system operates in TDD, a UE transmits one multiplexedACK/NACK signal for a plurality of PDSCHs received through subframes atdifferent timings. Specifically, the UE transmits one multiplexedACK/NACK signal for a plurality of PDSCHs using an ACK/NACK channelselection scheme (simply, channel selection scheme). The ACK/NACKchannel selection scheme is also referred to as a PUCCH selectionscheme. When the UE receives a plurality of DL data in the ACK/NACKchannel selection scheme, the UE occupies a plurality of UL physicalchannels in order to transmit a multiplexed ACK/NACK signal. Forexample, when the UE receives a plurality of PDSCHs, the UE can occupythe same number of PUCCHs as the PDSCHs using a specific CCE of a PDCCHwhich indicates each PDSCH. In this case, the UE can transmit amultiplexed ACK/NACK signal using combination of which one of theoccupied PUCCHs is selected and modulated/coded results applied to theselected PUCCH.

Table 3 shows an ACK/NACK channel selection scheme defined in the LTEsystem.

TABLE 3 HARQ-ACK(0), HARQ-ACK(1), Subframe HARQ-ACK(2), HARQ-ACK(3) n⁽¹⁾_(PUCCH,X) b(0), b(1) ACK, ACK, ACK, ACK n⁽¹⁾ _(PUCCH,1) 1, 1 ACK, ACK,ACK, NACK/DTX n⁽¹⁾ _(PUCCH,1) 1, 0 NACK/DTX, NACK/DTX, NACK, DTX n⁽¹⁾_(PUCCH,2) 1, 1 ACK, ACK, NACK/DTX, ACK n⁽¹⁾ _(PUCCH,1) 1, 0 NACK, DTX,DTX, DTX n⁽¹⁾ _(PUCCH,0) 1, 0 ACK, ACK, NACK/DTX, NACK/DTX n⁽¹⁾_(PUCCH,1) 1, 0 ACK, NACK/DTX, ACK, ACK n⁽¹⁾ _(PUCCH,3) 0, 1 NACK/DTX,NACK/DTX, NACK/DTX, n⁽¹⁾ _(PUCCH,3) 1, 1 NACK ACK, NACK/DTX, ACK,NACK/DTX n⁽¹⁾ _(PUCCH,2) 0, 1 ACK, NACK/DTX, NACK/DTX, ACK n⁽¹⁾_(PUCCH,0) 0, 1 ACK, NACK/DTX, NACK/DTX, NACK/DTX n⁽¹⁾ _(PUCCH,0) 1, 1NACK/DTX, ACK, ACK, ACK n⁽¹⁾ _(PUCCH,3) 0, 1 NACK/DTX, NACK, DTX, DTXn⁽¹⁾ _(PUCCH,1) 0, 0 NACK/DTX, ACK, ACK, NACK/DTX n⁽¹⁾ _(PUCCH,2) 1, 0NACK/DTX, ACK, NACK/DTX, ACK n⁽¹⁾ _(PUCCH,3) 1, 0 NACK/DTX, ACK,NACK/DTX, NACK/DTX n⁽¹⁾ _(PUCCH,1) 0, 1 NACK/DTX, NACK/DTX, ACK, ACKn⁽¹⁾ _(PUCCH,3) 0, 1 NACK/DTX, NACK/DTX, ACK, NACK/DTX n⁽¹⁾ _(PUCCH,2)0, 0 NACK/DTX, NACK/DTX, NACK/DTX, ACK n⁽¹⁾ _(PUCCH,3) 0, 0 DTX, DTX,DTX, DTX N/A N/A

In Table 3, HARQ-ACK(i) indicates the HARQ ACK/NACK/DTX result of ani-th data unit (0≦i≦3). DTX (Discontinuous Transmission) represents thatthere is no transmission of a data unit corresponding to HARQ-ACK(i) orthe UE does not detect the data unit corresponding to HARQ-ACK(i).Maximum 4 PUCCH resources (i.e., n⁽¹⁾ _(PUCCH,0) to n⁽¹⁾ _(PUCCH,3)) canbe occupied for each data unit. The multiplexed ACK/NACK signal istransmitted through one PUCCH resource selected from the occupied PUCCHresources. In Table 3, n⁽¹⁾ _(PUCCH,x) represents a PUCCH resourceactually used for ACK/NACK transmission, and b(0)b(1) indicates two bitstransmitted through the selected PUCCH resource, which are modulatedusing QPSK. For example, when the UE has decoded 4 data unitssuccessfully, the UE transits bits (1, 1) to a BS through a PUCCHresource linked with n⁽¹⁾ _(PUCCH,1). Since combinations of PUCCHresources and QPSK symbols cannot represent all available ACK/NACKsuppositions, NACK and DTX are coupled except some cases (NACK/DTX,N/D).

FIG. 11 illustrates a Carrier Aggregation (CA) communication system. Touse a wider frequency band, an LTE-A system employs CA (or bandwidthaggregation) technology which aggregates a plurality of UL/DL frequencyblocks to obtain a wider UL/DL bandwidth. Each frequency block istransmitted using a Component Carrier (CC). The CC can be regarded as acarrier frequency (or center carrier, center frequency) for thefrequency block.

Referring to FIG. 11, a plurality of UL/DL CCs can be aggregated tosupport a wider UL/DL bandwidth. The CCs may be contiguous ornon-contiguous in the frequency domain. Bandwidths of the CCs can beindependently determined. Asymmetrical CA in which the number of UL CCsis different from the number of DL CCs can be implemented. For example,when there are two DL CCs and one UL CC, the DL CCs can correspond tothe UL CC in the ratio of 2:1. A DL CC/UL CC link can be fixed orsemi-statically configured in the system. Even if the system bandwidthis configured with N CCs, a frequency band that a specific UE canmonitor/receive can be limited to M (<N) CCs. Various parameters withrespect to CA can be set cell-specifically, UE-group-specifically, orUE-specifically. Control information may be transmitted/received onlythrough a specific CC. This specific CC can be referred to as a PrimaryCC (PCC) (or anchor CC) and other CCs can be referred to as SecondaryCCs (SCCs).

LTE-A uses the concept of a cell in order to manage radio resources. Thecell is defined as a combination of DO resources and UL resources. Here,the UL resources are not an essential part. Accordingly, the cell can beconfigured with DL resources only, or DL resources and UL resources.When CA is supported, the linkage between a carrier frequency (or DL CC)of a DL resource and a carrier frequency (or UL CC) of a UL resource canbe designated by system information. A cell operating at a primaryfrequency (or PCC) can be referred to as a Primary Cell (PCell) and acell operating at a secondary frequency (or SCC) can be referred to as aSecondary Cell (SCell). The PCell is used for a UE to perform an initialconnection establishment procedure or a connection re-establishmentprocedure. The PCell may refer to a cell designated during a handoverprocedure. The SCell can be configured after RRC connection isestablished and used to provide additional radio resources. The PCelland the SCell can be called a serving cell. Accordingly, for a UE thatdoes not support CA while being in an RRC connected state, only oneserving cell configured with a PCell exists. Conversely, for a UE thatis in an RRC Connected state and supports CA, one or more serving cellsincluding a PCell and a SCell are provided. For CA, a network canconfigure one or more SCells for a UE that supports CA in addition to aPCell initially configured during a connection establishment procedureafter an initial security activation procedure.

When cross-carrier scheduling (or cross-CC scheduling) is applied, aPDCCH for DL allocation can be transmitted through DL CC#0 and a PDSCHcorresponding thereto can be transmitted through DL CC#2. For cross-CCscheduling, introduction of a Carrier Indicator Field (CIF) can beconsidered. The presence or absence of a CIF in a PDCCH can be setsemi-statically and UE-specifically (or UE-group-specifically) accordingto higher layer signaling (e.g. RRC signaling). The base line of PDCCHtransmission is summarized as follows.

-   -   CIF disabled: A PDCCH on a DL CC allocates a PDSCH resource on        the same DL CC or allocates a PUSCH resource on a linked UL CC.    -   CIF enabled: A PDCCH on a DL CC can allocate a PDSCH or a PUSCH        on a specific UL/DL CC from among a plurality of aggregated        DL/UL CCs using the CIF.

When a CIF is present, a BS can allocate a PDCCH monitoring DL CC set inorder to reduce BD complexity of a UE. The PDCCH monitoring DL CC setincludes one or more DL CCs as part of aggregated DL CCs, and the UEdetects/decodes a PDCCH only on DL CCs corresponding to the DL CC set.The PDCCH monitoring DL CC set can be determined UE-specifically,UE-group-specifically or cell-specifically. The term “PDCCH monitoringDL CC” can be replaced by equivalent terms “monitoring carrier”,“monitoring cell”, etc. In addition, the term “aggregated CC” for a UEcan be replaced by terms “serving CC”, “serving carrier”, “servingcell”, etc.

FIG. 12 illustrates scheduling when a plurality of carriers isaggregated. It is assumed that 3 DL CCs are aggregated and DL CC A isset to a PDCCH monitoring DL CC. DL CC A, DL CC B and DL CC C can becalled serving CCs, serving carriers, serving cells, etc. In case of CIFdisabled, a DL CC can transmit only a PDCCH that schedules a PDSCHcorresponding to the DL CC without a CIF. When the CIF is enabledaccording to UE-specific (or UE-group-specific or cell-specific) higherlayer signaling, DL CC A (monitoring DL CC) can transmit not only aPDCCH that schedules the PDSCH corresponding to the DL CC A but alsoPDCCHs that schedule PDSCHs of other DL CCs. In this case, DL CC B andDL CC C that are not set to a PDCCH monitoring DL CCs do not deliverPDCCHs. LTE-A considers transmission of a plurality of ACK/NACKinformation/signals with respect to a plurality of PDSCHs, which aretransmitted through a plurality of DL CCs, through a specific UL CC. Toachieve this, it can be considered to joint-code (Reed-Muller code,Tail-biting convolutional code, etc.) a plurality of ACK/NACKs andtransmit a plurality of ACK/NACK information/signals using PUCCH format2, or a new PUCCH format (referred to as an Enhanced PUCCH (E-PUCCH) orPUCCH format 3), distinguished from ACK/NACK transmission using PUCCHformat 1a/1b in the LTE system. PUCCH format 3 includes the followingblock-spreading based PUCCH format. After joint coding, ACK/NACKtransmission using PUCCH format 2/PUCCH format 3 is exemplary, and PUCCHformat 2/PUCCH format 3 can be used without being limited to UCItransmission. For example, PUCCH format 2/PUCCH format 3 can be used totransmit ACK/NACK, CSI (e.g. CQI, PMI, RI, PTI, etc.), SR, or two oremore thereof. Accordingly, PUCCH format 2/PUCCH format 3 can be used totransmit joint-coded UCI codewords irrespective of type/number/size ofUCI.

FIG. 13 illustrates a block-spreading-based PUCCH format 3 at a slotlevel. In PUCCH format 2 of LTE, one symbol sequence (d0, d1, d2, d3, ord4) is transmitted over the time domain and UE multiplexing is performedusing CS (α_(cs,x), x=0, 1, 2, 3, 4) of a Constant-Amplitude ZeroAuto-Correlation (CAZAC) sequence r_(u,0), as shown in FIG. 6. In theblock-spreading based PUCCH format 3, one symbol sequence is transmittedover the frequency domain and UE multiplexing is performed usingOrthogonal Cover Code (OCC) based time-domain spreading. That is, thesymbol sequence is time-domain-spread using the OCC and transmitted.Control signals of a plurality of UEs can be multiplexed on the same RBusing the OCC.

Referring to FIG. 13, 5 SC-FDMA symbols (i.e., UCI data part) aregenerated from one symbol sequence {d1, d2, . . . } using a length-5(Spreading Factor (SF)=5) OCC (C1, C2, C3, C4, C5). The symbol sequence{d1, d2, . . . } may be a modulation symbol sequence or a codeword bitsequence. When the symbol sequence {d1, d2, . . . } corresponds to thecodeword bit sequence, The block diagram of FIG. 13 further includes amodulation block. In FIG. 13, while 2 RS symbols (i.e., RS part) areused in one slot, it is possible to consider various applicationsincluding a scheme of using an RS part composed of 3 RS symbols and aUCI data part configured using an OCC with SF=4. Here, an RS symbol canbe generated from a CAZAC sequence having a specific cyclic shift. An RScan be transmitted in such manner that a specific OCC is applied to(multiplied by) a plurality of RS symbols in the time domain.Block-spread UCI is subjected to Fast Fourier Transform (FFT) andInverse FFT (IFFT) for each SC-FDMA symbol and transmitted to a network.That is, the block-spreading scheme modulates control information usingSC-FDMA, distinguished from PUCCH format 1 or 2a/2b of LTE.

FIG. 14 illustrates PUCCH format 3 at a subframes level.

Referring to FIG. 14, in slot 0, symbol sequence {d′0, d′1, . . . ,d′11} is mapped to a subcarrier of one SC-FDMA symbol and mapped to 5SC-FDMA symbols according to block spreading using OCC C1 to C5.Similarly, in slot 1, symbol sequence {d′12, d′13, . . . , d′23} ismapped to a subcarrier of one SC-FDMA symbol and mapped to 5 SC-FDMAsymbol according to block-spreading using ODD C1 to C5. Here, symbolsequences {d′0, d′1, . . . , d′11} and {d′12, d′13, . . . , d′23} inslots 0 and 1 represent symbol sequence {d1, d2, . . . }, shown in FIG.14, which has been subjected to FFT or FFT/IFFT. When symbol sequence{d′0, d′1, . . . , d′11} or {d′12, d′13, . . . , d′23} corresponds tosymbol sequence {d1, d2, . . . } which has been subjected to FFT, IFFTis additionally applied to symbol sequence {d′12, d′13, . . . , d′23} or{d′12, d′13, . . . , d′23} in order to generate SC-FDMA symbols. Theentire symbol sequence {d′0, d′1, . . . , d′23} is generated byjoint-coding one or more pieces of UCI, and the first half {d′0, d′1, .. . , d′11} is transmitted through slot 0 and the remaining {d′12, d′13,. . . , d′23} is transmitted through slot 1. The OCC can be changedbased on slot and UCI data can be scrambled for each SC-FDMA symbol.

In the following, a channel-coding based UCI (e.g. a plurality ofACK/NACKs) transmission scheme using PUCCH format 2 or E-PUCCH format(or PUCCH format 3) is referred to as “multi-bit UCI coding”transmission scheme for convenience of description. For example, themulti-bit UCI coding transmission scheme joint-codes ACK/NACK signals orDTX information (indicating that no PDCCH is received/detected) withrespect to PDSCHs and/or PDCCHs that indicate Semi-Persistent Scheduling(SPS) release of a plurality of DL cells and/or to generate a codedACK/NACK block, and transmits the coded ACK/NACK block. If a UE operatesin a Single User-Multiple Input Multiple Output (SU-MIMO) mode in a DLcell and receives 2 codewords, 4 feedback states of ACK/ACK, ACK/NACK,NACK/ACK, and NCK/NACK, or five feedback states additionally includingDTX can be present for the cell. If the UE receives a single codeword, 3feedback states of ACK, NACK and DTX can be present (2 feedback statesof ACK and NACK/DTX can be present if NACK and DTX are equallyprocessed). Accordingly, when the UE aggregates maximum 5 DL cells andoperates in the SU-MIMO mode, maximum 5⁵ feedback states can be present.Therefore, a required ACK/NACK payload size is at least 12 bits. If DTXand NACK are equally handled, the number of feedback states becomes 4⁵and the required ACK/NACK payload size is at least 10 bits.

An ACK/NACK multiplexing (i.e., ACK/NACK channel selection) method(refer to Table 3) applied to LTE TDD employs an implicit ACK/NACKchannel selection scheme using a PUCCH resource corresponding to a PDCCHthat schedules a PDSCH of a UE (i.e., PUCCH resource linked with thesmallest CCE index) so as to secure PUCCH resources for the UE. However,when the implicit scheme is applied using PUCCH resources in differentRBs, performance deterioration may occur. Accordingly, the LTE-A systemadditionally considers “explicit ACK/NACK channel selection” scheme thatuses PUCCH resources (preferably, a plurality of PUCCH resources in thesame RB or consecutive RBs) previously reserved for UEs through RRCsignaling. Furthermore, the LTE-A system considers ACK/NACK transmissionthrough one UE-specific UL cell (e.g. PCell).

Table 4 shows designation of PUCCH resources for HARQ-ACK.

TABLE 4 Value of HARQ-ACK resource for PUCCH (ARI) n_(PUCCH) 00 FirstPUCCH resource value configured by higher layer 01 Second PUCCH resourcevalue configured by higher layer 10 Third PUCCH resource valueconfigured by higher layer 11 Fourth PUCCH resource value configured byhigher layer

ARI represents an ACK/NACK resource indicator. In Table 4, the higherlayer includes RRC layer and an ARI value can be designated by a PDCCHthat delivers a DL grant. For example, the ARI value can be designatedusing an SCell PDCCH and/or a Transmit Power Control (TPC) field of oneor more PCell PDCCHs that do not correspond to DAI initial value.

FIG. 15 illustrates an example of dropping periodic CSI when a subframefor multiple ACK/NACK transmission and a subframe for periodic CSItransmission collide. In this example, it is assumed that a CSIreporting period is set to 5 msec (i.e. 5 subframes).

Referring to FIG. 15, the CSI is periodically transmitted. In thisexample, the CSI needs to be transmitted in subframes #5 and #10. AnACK/NACK transmission time depends on downlink scheduling. In thisexample, ACK/NACK is transmitted in subframes #4, #8 and #10. When theACK/NACK transmission time and a CSI transmission time do not collide, aUE transmits the ACK/NACK and CSI in the corresponding subframes. If theACK/NACK transmission time and a CSI transmission time collide, the UEmay drop the CSI in order to maintain single carrier properties. Forexample, only ACK/NACK can be transmitted and CSI feedback can bedropped in subframe #10 in which the ACK/NACK transmission time and theCSI transmission time overlap.

If single carrier property is not required in UL transmission anddifferent PUCCH formats and/or different PUCCH resources are assignedfor the ACK/NACK and CSI feedback, the UE can simultaneously transmitthe ACK/NACK and CSI.

FIG. 16 illustrates an example of simultaneously transmitting ACK/NACKand an SR by embedding the SR in a PUCCH format 2a/2b resource thatcarries multiple ACK/NACKs. This example is based on the assumption thata subframe (i.e. SR subframe) interval is set to 5 msec (i.e. 5subframes) for SR transmission.

Referring to FIG. 16, a subframe capable of transmitting the SR isperiodically set. In this example, the SR can be transmitted insubframes #5 and #10. The UE needs to simultaneously transmit multipleACK/NACKs and SR in the subframes #5 and #10. In the normal CP case,1-bit SR information (e.g. positive SR:1, negative SR:0) is used tomodulate the second RS symbol of PUCCH format 2a/2b (similar to FIG. 7),and thus the SR and ACK/NACK can be simultaneously transmitted. When thePUCCH format 2a/2b resource is configured/occupied for CSI feedback, the1-bit SR information is used to modulate the second RS symbol of PUCCHformat 2a/2b, and thus the SR and CSI can be simultaneously transmitted.In extended CP case, the 1-bit SR information can be joint coded (e.g.coding using a RM code, TBCC, etc.) with the ACK/NACK or CSI, and twoUCIs (i.e. SR+ACK/NACK or SR+CSI) can be transmitted on the same PUCCHformat 2a/2b resource (similar to FIG. 8).

In this case, the SR can be embedded in PUCCH format 2 for CSItransmission only when ACK/NACK transmission is not required at thecorresponding time (i.e. time when SR transmission and CSI transmissionoverlap).

In LTE, when only ACK/NACK information about a single CC is present andthe ACK/NACK transmission time and CSI transmission time collide, asdescribed above, the ACK/NACK information can be transmitted through RSmodulation (in case of normal CP) of PUCCH format 2 for transmitting theCSI (refer to FIG. 7) or through joint coding (in case of extended CP)(refer to FIG. 8). In LTE-A, an E-PUCCH format (or PUCCH format 3) based“multi-bit ACK/NACK coding” or “ACK/NACK channel selection” scheme isconsidered for transmission of multiple ACK/NACKs for multiple CCs, asdescribed above. Considering transmission of ACK/NACK through these twoschemes, it may be desirable to abandon (drop) CSI transmission andtransmit ACK/NACK only when CSI transmission time through PUCCH format 2and the ACK/NACK transmission time are overlapped. That's why ACK/NACKperformance deterioration may occur when the multiple ACK/NACKs formultiple CCs are transmitted through RS modulation of PUCCH format 2that transmits CSI or through joint coding as in LTE. However,unconditional CSI drop when the ACK/NACK transmission time and CSItransmission time overlap may cause problems including a delay in DLscheduling due to lack of information about the CSI.

A description will be given of a method for efficiently transmitting UCIwhen multiple UCI transmission times collide. First of all, termsrelating to the present invention are arranged.

-   -   HARQ-ACK: This represents a reception response result for DL        transmission (e.g. PDSCH or SPS release PDCCH), that is, an        ACK/NACK/DTX response (simply, ACK/NACK response). The        ACK/NACK/DTX response represents ACK, NACK, DTX or NACK/DTX.        “HARQ-ACK for a specific CC” or “HARQ-ACK of a specific CC”        denotes an ACK/NACK response to a DL signal (e.g. PDSCH) with        respect to the CC. An ACK/NACK state means a combination        corresponding to a plurality of HARQ-ACKs. Here, a PDSCH can be        replaced by a TB or a CW.    -   PUCCH index: This corresponds to a PUCCH resource. For example,        the PUCCH index indicates a PUCCH resource index. The PUCCH        resource index is mapped to at least one of an Orthogonal Cover        (OC), Cyclic Shift (CS) and PRB. When the ACK/NACK channel        selection scheme is applied, the PUCCH index includes a PUCCH        (resource) index for PUCCH format 1b.    -   PUCCH resource linked to CC: This represents a PUCCH resource        (refer to Equation 1, implicit PUCCH resource) linked to a PDCCH        corresponding to a PDSCH on a CC, or a PUCCH resource (explicit        PUCCH resource) designated/allocated by the PDCCH corresponding        to the PDSCH on the CC. The PUCCH resource in the explicit PUCCH        resource scheme can be designated/allocated using an ACK/NACK        Resource Indicator (ARI).    -   ARI: This is used to indicate a PUCCH resource. For example, the        ARI can be used to indicate a resource modification value (e.g.        offset) with respect to a specific PUCCH resource (configured by        a higher layer). Furthermore, the ARI can be used to indicate a        specific PUCCH resource (group) index in a PUCCH resource        (group) set (configured by a higher layer). The ARI can be        included in a TPC field of a PDCCH corresponding to a PDSCH on        an SCC. PUCCH power control is performed in a TPC field in a        PDCCH (that is, PDCCH corresponding to a PDSCH on a PCC) that        schedules the PCC. The ARI can be included in a TPC field of a        PDCCH other than a PDCCH that has a Downlink Assignment Index        (DAI) initial value and schedules a specific cell (e.g. PCell).        The ARI is interchangeably used with a HARQ-ACK resource        indication value.    -   Implicit PUCCH resource: This represents a PUCCH resource/index        linked to the smallest CCE index of a PDCCH that schedules a PCC        (refer to Equation 1).    -   Explicit PUCCH resource: This can be indicated using the ARI.        When the ARI cannot be applied, the explicit PUCCH resource may        be a PUCCH resource previously fixed by higher layer signaling.        All explicit PUCCH indexes allocated to one UE can be        contiguous, or indexes for resource groups can be contiguous.        Otherwise, all the indexes can be independently allocated.    -   PDCCH scheduling CC: This represents a PDCCH that schedules a        PDSCH on a CC, that is, a PDCCH corresponding to a PDSCH on the        CC.    -   PCC PDCCH: This represents a PDCCH that schedules a PCC. That        is, the PCC PDCCH indicates a PDCCH corresponding to a PDSCH on        the PCC. When it is assumed that cross-carrier scheduling is not        allowed for the PCC, the PCC PDCCH is transmitted only on the        PCC.    -   SCC PDCCH: This represents a PDCCH that schedules an SCC. That        is, the SCC PDCCH indicates a PDCCH corresponding to a PDSCH on        the SCC. When cross-carrier scheduling is allowed for the SCC,        the SCC PDCCH can be transmitted on the PCC. On the other hand,        when cross-carrier scheduling is not allowed for the SCC, the        SCC PDCCH is transmitted only on the SCC.    -   SR subframe: This represents a UL subframe configured for SR        transmission. According to implementation, The SR subframe can        be defined as a subframe in which SR information is transmitted,        or a subframe allowed to transmit the SR information. The SR        subframe can be specified according to higher layer signaling        (e.g. period, offset).    -   CSI subframe: This represents an uplink subframe configured for        CSI transmission. The CSI subframe can be specified according to        higher layer signaling (e.g. period, offset).

UCI Transmission in FDD System

The present embodiment proposes a scheme of dropping CSI according topredetermined conditions and transmitting only ACK/NACK through a PUCCHformat/resource (e.g. PUCCH format 3) for ACK/NACK, or simultaneouslytransmitting the CSI and ACK/NACK by embedding the ACK/NACK in PUCCHformat 2/2a/2b, if the ACK/NACK transmission time and CSI transmissiontime collide when PUCCH format 3 based multi-bit ACK/NACK coding andimplicit and/or explicit PUCCH resource based ACK/NACK channel selectionscheme are applied for transmission of multiple ACK/NACKs. The ACK/NACKcan be embedded in PUCCH format 2/2a/2b through RS modulation (in caseof normal CP) in a PUCCH format (refer to FIG. 7) or through jointcoding (in case of extended CP) (refer to FIG. 8). Here, thepredetermined conditions includes a case in which transmission of onlyACK/NACK information about one specific CC (e.g. DL PCC) (or DL PCell)is required at the CSI transmission time. For example, the predeterminedconditions include a case in which the CSI transmission time correspondsto subframe n and the UE receives one PDSCH through one specific CC onlyin subframe n−4. Here, the PDSCH is used to represent both a PDSCH andPDCCH that require ACK/NACK feedback. For example, the PDSCH is used torepresent a PDCCH that orders SPS release. The proposed scheme isreferred to as “Alt 1” for convenience of description. Usage/non-usageof this scheme may be UE-specifically signaled through higher layer(e.g. RRC) signaling.

The above scheme may be applied to a case in which NACK or DTX isidentified to all PDSCHs received through all secondary DL CCs otherthan the primary DL CC at the CSI transmission time without dropping theCSI. That is, it is possible to simultaneously transmit the CSI andACK/NACK by embedding ACK/NACK for the primary DL CC in PUCCH format2/2a/2b.

It is possible to signal whether simultaneous transmission of the CSIand ACK/NACK and simultaneous transmission of SRS and ACK/NACK arepermitted through a higher layer. Particularly, when simultaneoustransmission of the SRS and ACK/NACK is permitted, a plurality ofspecific subframes may be present, which are set to use a shortenedPUCCH format for ACK/NACK transmission. The shortened PUCCH format meansa PUCCH format that transmits a UL signal using only SC-FDMA (or OFDM)symbols other than an SC-FDMA (or OFDM) symbol (e.g. the last symbol ofa subframe) capable of transmitting the SRS in a subframe in which acorresponding PUCCH is transmitted. For reference, a normal PUCCH formatmeans a PUCCH format that performs UL signal transmission using up toSC-FDMA (or OFDM) symbol (e.g. the last symbol of a subframe) capable oftransmitting the SRS in a subframe. When the CSI, ACK/NACK and SRS needto be transmitted at the same time (i.e. in collided subframes) whilesimultaneous transmission of the CSI and ACK/NACK is permitted in a CCaggregation based FDD system, the following UE operations can beconsidered on the basis of Alt 1 according to whether simultaneoustransmission of the SRS and ACK/NACK is permitted.

-   -   When simultaneous transmission of SRS and A/N is permitted    -   In case of using the shortened PUCCH format in collided        subframes    -   Case #1) Only PDSCH for a PCC is received: It is possible to        drop the SRS and simultaneously transmit the CSI and A/N in        PUCCH format 2/2a/2b using Alt 1.    -   Case #2) All cases other than case #1: It is possible to drop        the CSI and simultaneously transmit the SRS and A/N using the        shortened PUCCH format. Considering UCI priority defined in LTE,        SRS drop can be considered because the CSI has priority higher        than the SRS. However, it is advantageous to transmit the SRS        because the CSI is dropped according to collision of the CSI and        A/N in cases other than case #1.    -   In case that the shortened PUCCH format is not used in collided        subframes    -   Case #1) Only PDSCH for the PCC is received: It is possible to        drop the SRS, and simultaneously transmit the CSI and A/N in        PUCCH format 2/2a/2b using Alt 1.    -   Case #2) All cases other than case #1: It is possible to drop        the CSI and SRS, and transmit A/N using the normal PUCCH format.    -   When simultaneous transmission of SRS and A/N is not permitted    -   Case #1) Only PDSCH for the PCC is received: It is possible to        drop the SRS, and simultaneously transmit the CSI and A/N in        PUCCH format 2/2a/2b using Alt 1.    -   Case #2) All cases other than case #1: It is possible to drop        the CSI and SRS, and transmit A/N using the normal PUCCH format.

In case of CC aggregation based FDD, the following UE operations can beconsidered when simultaneous transmission of the CSI and A/N is requiredaccording to a combination of PUCCH/PUSCH simultaneous transmissionpermission (referred to as “PUCCH+PUSCH ON” forconvenience)/nonpermission (referred to as “PUCCH+PUSCH OFF” forconvenience) and CSI+A/N simultaneous transmission permission (referredto as “CSI+A/N ON” for convenience)/nonpermission (referred to as“CSI+A/N OFF” for convenience) on the basis of Alt 1.

-   -   In case of PUCCH+PUSCH OFF and CSI+A/N OFF    -   When no PUSCH is transmitted        -   It is possible to drop the CSI and transmit A/N over a            PUCCH.    -   When a PUSCH is transmitted        -   It is possible to piggy back the CSI and A/N on the PUSCH to            transmit the CSI and A/N. In this case, no PUCCH is            transmitted.    -   In case of PUCCH+PUSCH OFF and CSI+A/N ON    -   When no PUSCH is transmitted        -   Case #1) Only PDSCH for the PCC is received: It is possible            to simultaneously transmit the CSI and A/N over the PUCCH            using Alt 1.        -   Case #2) All cases other than case #1: It is possible to            drop the CSI and transmit A/N over the PUCCH.    -   When a PUSCH is transmitted        -   It is possible to piggy back the CSI and A/N on the PUSCH to            transmit the CSI and A/N. In this case, no PUCCH is            transmitted.    -   In case of PUCCH+PUSCH ON and CSI+A/N OFF    -   When no PUSCH is transmitted        -   It is possible to drop the CSI and transmit A/N over the            PUCCH.    -   When a PUSCH is transmitted        -   It is possible to piggy back the CSI on the PUSCH and            transmit A/N over the PUCCH.    -   In case of PUCCH+PUSCH ON and CSI+A/N ON    -   When no PUSCH is transmitted        -   Case #1) Only PDSCH for the PCC is received: It is possible            to simultaneously transmit the CSI and A/N over the PUCCH            using Alt 1.        -   Case #2) All cases other than case #1): It is possible to            drop the CSI and transmit A/N over the PUCCH.    -   When a PUSCH is transmitted        -   Case #1) Only PDSCH for the PCC is received: It is possible            to simultaneously transmit the CSI and A/N over the PUCCH            using Alt 1.        -   Case #2) All cases other than case #1: It is possible to            piggy back the CSI on the PUSCH and transmit A/N over the            PUCCH.

UCI Transmission in TDD System

It is apparent that the aforementioned proposed scheme is applicable toa CC aggregation based TDD system as well as the CC aggregation basedFDD system. The proposed scheme used in a TDD system will now bedescribed in detail. For multi-ACK/NACK transmission, E-PUCCH formatbased multi-bit UCI coding and implicit and/or explicit PUCCH resourcebased ACK/NACK (A/N) channel selection scheme may be used. In a TDDsystem, multiple ACK/NACKs may be generated according to a plurality ofCC configurations, a plurality of DL subframe configurationscorresponding to one UL subframe in which ACK/NACK is transmitted, or acombination thereof.

TDD Scheme 1

This scheme drops CSI and transmits only ACK/NACK, or embeds ACK/NACKcounter information in PUCCH format 2/2a/2b, according to predeterminedconditions when an ACK/NACK transmission time and a CSI transmissiontime collide in a TDD system. When the CSI is dropped, the ACK/NACK canbe transmitted using a multi-bit UCI coding scheme (using E-PUCCH format(or PUCCH format 3), for example) or an ACK/NACK (A/N) channel selectionscheme (using PUCCH format 1b, for example), preferably, the ACK/NACK(A/N) channel selection scheme (using PUCCH format 1b).

-   -   ACK counter: This indicates the total number of ACKs (or the        number of some of the ACKs) for all received PDSCHs (in view of        ACK/NACK feedback, PDSCHs may include a PDCCH (e.g. a PDCCH that        orders SPS release) that requires ACK/NACK feedback in the        specification). Specifically, the number of ACKs can be signaled        by a UE when only ACKs are generated for all received PDSCHs        without detection of DTX, and the number of ACKs can be counted        as 0 (or processed as DTX or NACK) when the UE detects DTX or        when the received PDSCHs include at least one NACK.

Table 5 shows the number of ACKs and bit values b(0)b(1) defined in LTE.

TABLE 5 Number of ACK among multiple (U_(DAI) + N_(SPS)) ACK/NACKresponses b(0), b(1) 0 or None (UE detects that at least 0, 0 one DLassignment is missed) 1 1, 1 2 1, 0 3 0, 1 4 1, 1 5 1, 0 6 0, 1 7 1, 1 81, 0 9 0, 1

In Table 5, U_(DAI) represents the number of PDCCH(s) having allocatedPDSCH transmission(s) and PDCCHs that order DL SPS release, which aredetected by a UE in DL subframe(s) n−k (kεK). N_(SPS) denotes the numberof PDSCH transmissions having no PDCCH corresponding thereto in DLsubframe(s) n−k (kεK). UL subframe n corresponds to a subframe thatrequires ACK/NACK transmission.

K is given according to UL-DL configuration. Table 6 shows K: {k₀, k₁, .. . , k_(M-1)} defined in LTE TDD. Here, M denotes the number of DLsubframes corresponding to one UL subframe. Accordingly, a TDDconfiguration in which (the number of DL subframes): (the number of ULsubframes)=M:1 means a TDD configuration set such that ACK/NACKinformation about data/control channel(s) received through M DLsubframe(s) is fed back through one UL subframe. The value M may dependon the UL subframe.

TABLE 6 UL-DL Configu- Subframe n ration 0 1 2 3 4 5 6 7 8 9 0 — — 6 — 4— — 6 — 4 1 — — 7, 6 4 — — — 7, 6 4 — 2 — — 8, 7, 4, 6 — — — — 8, 7, — —4, 6 3 — — 7, 6, 11 6, 5 5, 4 — — — — — 4 — — 12, 8, 7, 6, 5, — — — — —— 11 4, 7 5 — — 13, 12, 9, — — — — — — — 8, 7, 5, 4, 11, 6 6 — — 7 7 5 —— 7 7 —

Embedding ACK/NACK counter information to PUCCH format 2/2a/2b can beachieved through RS modulation of PUCCH format (refer to FIG. 7) (incase of normal CP) or joint coding (refer to FIG. 8) (in case ofextended CP). In the present example, the predetermined conditionsinclude a case in which only transmission of ACK/NACK information aboutDL subframe(s) of one specific CC (e.g. DL PCC) (or DL PCell) isrequired at the CSI transmission time. For example, the predeterminedconditions include a case in which the CSI transmission time correspondsto subframe n and the UE receives a PDSCH only through one specific CCin subframe n−k. Here, the PDSCH means both a PDSCH and a PDCCH thatrequires ACK/NACK feedback. For example, the PDSCH may mean a PDCCH thatorders SPS release. Usage/non-usage of this scheme can beUE-specifically signaled through higher layer (RRC) signaling.

When a DAI (Downlink Assignment Index) independently operates for eachCC in TDD, it is possible to consider a case in which a DAI for only aPDSCH of a specific CC (e.g. PCC) is signaled through a PDCCH thatschedules the specific CC. A DAI may be a DAI-counter, e.g. a parameterthat indicates the order of scheduled PDSCHs on the basis of apredetermined order (e.g. order of DL subframes). When the DAI-counteris used, the ACK counter may signal 1) the number of ACKs only when thelast received DAI counter value is identical with a total of the numberof ACKs, or 2) the number of ACKs corresponding to a DAI-counter valuethat continuously increases from a DAI-counter initial value (PDSCHcorresponding thereto). Here, the DAI may have an initial value of 0 or1.

Table 7 shows an exemplary ACK counter. Table 7 shows a case in whichthe ACK counter is represented by 2 bits. The number of bits used torepresent the ACK counter can be set according to implementation examplein various manners.

TABLE 7 Number of ACK among multiple ACK/NACK responses b(0), b(1) 0 orNone (UE misses at least one DL assignment) 0, 0 (that is, DTX)) 1 1, 12 1, 0 3 0, 1 4 1, 1 4 1, 0 5 0, 1 6 1, 1 7 1, 0 8 0, 1 9 1, 1 0 1, 0

In a TDD configuration in which (the number of DL subframes): (thenumber of UL subframes)=M:1, when M is 2, it is possible to generate2-bit ACK/NACK information for PDSCHs (or PDSCHs corresponding to DAI=1and DAI=2 on the assumption that DAI starting with 1 is used) receivedthrough two DL subframes of a primary CC, and then the above-mentionedscheme (which transmits the 2-bit ACK/NACK information through RSmodulation of PUCCH format 2 for CSI transmission or through jointcoding) can be carried out without dropping CSI, only in a case in whichPDSCHs are received through only the primary CC. Here, when the primaryCC is configured as being a MIMO transmission mode, CW bundling may beapplied to a PDSCH (or a PDSCH corresponding to each DAI value) receivedthrough each DL subframe. CW bundling is a scheme of transmittingbundled 1-bit ACK/NACK information for PDSCH(s) of a CC configured withthe MIMO transmission mode (i.e. when a plurality of CWs are transmittedthrough a PDSCH, ACK is signaled only when all the CWs of the PDSCHcorrespond to ACK, and NACK is signaled in other cases).

When multi-bit ACK/NACK coding (i.e. E-PUCCH format (PUCCH format 3) isapplied for TDD ACK/NACK transmission, it is possible to use theaforementioned scheme without dropping CSI when PDSCHs received throughall secondary CCs other than the primary CC correspond to NACK or DTX atthe CSI transmission time. That is, ACK counter information aboutmultiple DL subframes of the primary CC can be transmitted through an RSsymbol (i.e. RS modulation) of PUCCH format 2 in which CSI istransmitted or through a payload (i.e. joint coding).

When ACK counter based ACK/NACK channel selection is applied for TDDACK/NACK transmission, it is possible to use the aforementioned schemewithout dropping CSI when the number of ACKs is 0 (NACK or DTX) for allsecondary CCs other than the primary CC at the CSI transmission time.That is, ACK counter information about multiple DL subframes of theprimary CC can be transmitted through an RS symbol (i.e. RS modulation)of PUCCH format 2 in which CSI is transmitted or through a payload (i.e.joint coding).

FIG. 17 illustrates an exemplary UCI transmission scheme according to anembodiment of the present invention. It is assumed that a UE isconfigured to use the A/N channel selection scheme. FIG. 17 illustratesa PUCCH resource allocation procedure focused on ACK/NACK and CSI. Thefollowing three cases can be considered for transmission of ACK/NACK andCSI.

-   -   Case 1: ACK/NACK is transmitted in a non-CSI subframe.    -   Case 2: ACK/NACK is transmitted in a CSI subframe, and a        predetermined condition is not satisfied.    -   Case 3: ACK/NACK is transmitted in a CSI subframe, and a        predetermined condition is satisfied.

Referring to FIG. 17, ACK/NACK is transmitted using the A/N channelselection scheme in case 1. Specifically, a UE selects one PUCCHresource corresponding to multiple HARQ-ACKs from a plurality of PUCCHresources and transmits bit values (e.g. b(0)b(1)) corresponding to themultiple HARQ-ACKs using the selected PUCCH resource (refer to Table 3).PUCCH format 1b may be used for the A/N channel selection scheme.

Cases 2 and 3 show a case in which ACK/NACK needs to be transmitted in aCSI subframe. Case 2 corresponds to a case in which a predeterminedcondition is not satisfied whereas case 3 corresponds to a case in whichthe predetermined condition is satisfied. The predetermined conditionincludes a case in which transmission of only ACK/NACK information aboutDL subframe(s) of one specific CC (e.g. DL PCC) (or DL PCell) isrequired at the CSI transmission time (i.e. CSI subframe). For example,the predetermined condition includes a case in which the CSItransmission time corresponds to subframe n and the UE receives adownlink signal that requires ACK/NACK feedback only through onespecific CC in subframe n−k. The downlink signal that requires ACK/NACKfeedback includes a PDSCH and a PDCCH that orders SPS release. When thepredetermined condition is not satisfied (i.e. in case 2), the UE dropsCSI and transmits ACK/NACK only. In this case, ACK/NACK can betransmitted using the A/N channel selection scheme. Conversely, when thepredetermined condition is satisfied (i.e. in case 3), the UE transmitsboth information that indicates the ACK/NACK counter and the CSI using asingle PUCCH. Specifically, the information indicating the ACK/NACKcounter can be embedded in the PUCCH format for CSI transmission andtransmitted. More specifically, the information indicating the ACK/NACKcounter can be loaded in the RS symbol (e.g. RS modulation) of PUCCHformat 2/2a/2b for CSI transmission (refer to FIG. 7) or in a payload(e.g. joint coding) (refer to FIG. 8) and transmitted.

TDD Scheme 2

This scheme drops CSI and transmits only ACK/NACK, or embeds ACK/NACK inPUCCH format 2/2a/2b, according to predetermined conditions when anACK/NACK transmission time and a CSI transmission time collide in a TDDsystem. When the CSI is dropped, the ACK/NACK can be transmitted using amulti-bit UCI coding scheme (e.g., using E-PUCCH format (or PUCCH format3)) or an ACK/NACK (A/N) channel selection scheme (e.g., using PUCCHformat 1b), preferably, the multi-bit UCI coding scheme (using E-PUCCHformat or PUCCH format 3). When both the CSI and ACK/NACK aretransmitted, TDD scheme 2 transmits full ACK/NACK information while TDDscheme 1 transmits compressed ACK/NACK information (e.g. ACK/NACKcounter information).

In this scheme, the predetermined conditions include a case in whichonly one PDSCH (when a SPS PDSCH is not present) corresponding to a DAIinitial value or the SPS PDSCH (when the SPS PDSCH is present) isreceived only through a primary CC (or PCell) in DL subframe(s)corresponding to a UL subframe (i.e. CSI subframe) for CSI transmission.For example, the predetermined conditions include a case in which theCSI transmission time corresponds to subframe n and a UE receives onlyone PDSCH (when a SPS PDSCH is not present) corresponding to the DAIinitial value or the SPS PDSCH (when the SPS PDSCH is present) onlythrough the primary CC in subframe n−k (n and n−k refers to Table 6).Here, the PDSCH means a PDSCH and a PDCCH that require ACK/NACKfeedback. For example, the PDSCH means a PDCCH that indicates SPSrelease. Usage/non-usage of TDD scheme 2 can be UE-specifically signaledthrough higher layer (RRC) signaling.

-   -   DAI: DAI-counter may be a parameter indicating the order of        PDSCHs scheduled based on a predetermined order (e.g. the order        of DL subframes). For example, when DL subframes #1, #2 and #3        correspond to one UL subframe and DL subframes #1 and #3 are        scheduled, DAI-counter values in PDCCHs corresponding to DL        subframes #1 and #3 can be signaled as an initial value and        ‘initial value+1’, respectively. The DAI initial value may be 0        or 1. Considering a 2-bit DAI-counter, modulo-4 operation can be        applied to DAI-counter values greater than 4. A DAI may be        assigned to each DL CC (DL cell).

FIG. 18 illustrates an exemplary UCI transmission scheme according to anembodiment of the present invention. It is assumed that the UE isconfigured to use the multi-bit UCI coding scheme (i.e. E-PUCCH format(PUCCH format 3)). FIG. 18 illustrates a PUCCH resource allocationprocedure focused on ACK/NACK and CSI. The following three cases can beconsidered for transmission of ACK/NACK and CSI.

-   -   Case 1: ACK/NACK is transmitted in a non-CSI subframe.    -   Case 2: ACK/NACK is transmitted in a CSI subframe, and a        predetermined condition is not satisfied.    -   Case 3: ACK/NACK is transmitted in a CSI subframe, and a        predetermined condition is satisfied.

Referring to FIG. 18, ACK/NACK is transmitted using the multi-bit UCIcoding scheme in case 1. Specifically, ACK/NACK is transmitted using theE-PUCCH format/resource described with reference to FIGS. 13 and 14. AHARQ-ACK PUCCH resource for the E-PUCCH format may be explicitlyallocated using ARI. As shown in Table 4, the HARQ-ACK PUCCH resourcefor the E-PUCCH format may be indicated by values of TPC (Transmit PowerControl) fields of one or more SCC PDCCHs.

Cases 2 and 3 correspond to a case in which ACK/NACK needs to betransmitted in a CSI subframe. Case 2 corresponds to a case in which apredetermined condition is not satisfied whereas case 3 corresponds to acase in which the predetermined condition is satisfied. For example, thepredetermined condition includes at least one of the followingconditions (1) to (3). Specifically, the predetermined conditionincludes at least one of the following conditions (1) to (3) forsubframe n−k when the CSI transmission time corresponds to subframe n.

-   -   (1) a single PDSCH transmission only on a PCell indicated by        detection of a PDCCH having a DAI initial value is present. The        DAI initial value is 0 or 1.    -   (2) a single PDCCH transmission only on the PCell that has the        DAI initial value and indicates an SPS release is present. The        DAI initial value is 0 or 1.    -   (3) a single PDSCH transmission only on the PCell where there is        not a corresponding PDCCH is present.

When the predetermined condition is not satisfied (case 2), the UE dropsCSI and transmits ACK/NACK only. In this case, the ACK/NACK can betransmitted using the E-PUCCH format/resource. When the predeterminedcondition is satisfied (case 3), the UE transmits both the ACK/NACK andCSI using a single PUCCH. Specifically, the ACK/NACK can be embedded ina PUCCH format for CSI transmission and transmitted. More specifically,the ACK/NACK can be loaded in the RS symbol (e.g. RS modulation) ofPUCCH format 2/2a/2b for CSI transmission (refer to FIG. 7) or in apayload (e.g. joint coding) (refer to FIG. 8) and transmitted.

In TDD scheme ½, it is possible to independently signal whether or notsimultaneous transmission of CSI and A/N and simultaneous transmissionof SRS and A/N are permitted. Particularly, when simultaneoustransmission of SRS and A/N is permitted, a plurality of specific ULsubframes configured to use the shortened PUCCH format for A/Ntransmission may be present. The shortened PUCCH format means a PUCCHformat that transmits a UL signal using only symbols other than anSC-FDMA (or OFDM) symbol capable of transmitting the SRS in a subframein which a corresponding PUCCH is transmitted. For reference, a normalPUCCH format means a PUCCH format that performs UL signal transmissionusing up to SC-FDMA (or OFDM) symbols (e.g. the last symbol of asubframe) capable of transmitting the SRS in a subframe.

When CSI, ACK/NACK and SRS need to be transmitted at the same time (i.e.in collided subframes) while simultaneous transmission of the CSI andACK/NACK is permitted in a CC aggregation based TDD system, thefollowing UE operations can be considered on the basis of TDD scheme ½according to whether or not simultaneous transmission of SRS andACK/NACK is permitted.

-   -   When simultaneous transmission of SRS and A/N is permitted    -   In case of using the shortened PUCCH format in collided        subframes        -   Case in which application of TDD scheme 1 is considered        -   Case #1) one or more PDSCHs are received only for PCC: It is            possible to drop the SRS and simultaneously transmit the CSI            and A/N in PUCCH format 2/2a/2b using TDD scheme 1.        -   Case #2) All cases other than case #1: It is possible to            drop the CSI and simultaneously transmit the SRS and A/N            using the shortened PUCCH format. Considering UCI priority            defined in LTE, SRS drop can be considered because the CSI            has a higher priority than the SRS. However, in cases other            than case #1, it is advantageous to transmit the SRS because            the CSI is dropped according to collision of the CSI and            A/N.        -   Case in which application of TDD scheme 2 is considered        -   Case #1) only one PDSCH (when SPS PDSCH is not present)            corresponding to a DAI initial value or only one SPS PDSCH            (when SPS PDSCH is present) is received only for PCC: It is            possible to drop the SRS and simultaneously transmit the CSI            and A/N in PUCCH format 2/2a/2b using TDD scheme 2.        -   Case #2) All cases other than case #1: It is possible to            drop the CSI and simultaneously transmit the SRS and A/N            using a shortened PUCCH format.    -   In case that the shortened PUCCH format is not used in collided        subframes        -   Case in which application of TDD scheme 1 is considered        -   Case #1) one or more PDSCHs are received only for PCC: It is            possible to drop the SRS and simultaneously transmit the CSI            and A/N in PUCCH format 2/2a/2b using TDD scheme 1.        -   Case #2) All cases other than case #1: It is possible to            drop the CSI and SRS, and transmit A/N using a normal PUCCH            format.        -   Case in which application of TDD scheme 2 is considered        -   Case #1) only one PDSCH (when SPS PDSCH is not present)            corresponding to a DAI initial value or only one SPS PDSCH            (when SPS PDSCH is present) is received only for PCC: It is            possible to drop the SRS and simultaneously transmit the CSI            and A/N in PUCCH format 2/2a/2b using TDD scheme 2.        -   Case #2) All cases other than case #1: It is possible to            drop the CSI and SRS, and transmit A/N using a normal PUCCH            format.    -   When simultaneous transmission of SRS and A/N is not permitted        -   Case in which application of TDD scheme 1 is considered        -   Case #1) one or more PDSCHs are received only for PCC: It is            possible to drop the SRS, and simultaneously transmit the            CSI and A/N in PUCCH format 2/2a/2b using TDD scheme 1.        -   Case #2) All cases other than case #1: It is possible to            drop the CSI and SRS, and transmit A/N using a normal PUCCH            format.    -   Case in which application of TDD scheme 2 is considered        -   Case #1) only one PDSCH (when SPS PDSCH is not present)            corresponding to a DAI initial value or only one SPS PDSCH            (when SPS PDSCH is present) is received only for PCC: It is            possible to drop the SRS, and simultaneously transmit the            CSI and A/N in PUCCH format 2/2a/2b using TDD scheme 2.        -   Case #2) All cases other than case #1: It is possible to            drop the CSI and SRS, and transmit A/N using a normal PUCCH            format.

In case of CC aggregation based TDD, the following UE operations can beconsidered when simultaneous transmission of CSI and A/N is requiredaccording to a combination of permission (referred to as “PUCCH+PUSCHON” for convenience)/non-permission (referred to as “PUCCH+PUSCH OFF”for convenience) of simultaneous transmission of PUCCH/PUSCH andpermission (referred to as “CSI+A/N ON” for convenience)/nonpermission(referred to as “CSI+A/N OFF” for convenience) of simultaneoustransmission of CSI+A/N over a PUCCH on the basis of the proposedschemes.

-   -   In case of PUCCH+PUSCH OFF and CSI+A/N OFF    -   When there is no PUSCH transmission        -   It is possible to drop CSI and transmit A/N through a PUCCH.    -   When there is a PUSCH transmission        -   It is possible to piggy back the CSI and A/N on the PUSCH to            transmit the CSI and A/N. In this case, no PUCCH is            transmitted.    -   In case of PUCCH+PUSCH OFF and CSI+A/N ON    -   When there is no PUSCH transmission        -   Case in which application of TDD scheme 1 is considered        -   Case #1) one or more PDSCHs are received only for PCC: It is            possible to simultaneously transmit the CSI and A/N through            a PUCCH using TDD scheme 1.        -   Case #2) All cases other than case #1: It is possible to            drop the CSI, and transmit A/N through a PUCCH.        -   Case in which application of TDD scheme 2 is considered        -   Case #1) only one PDSCH (when SPS PDSCH is not present)            corresponding to a DAI initial value or only one SPS PDSCH            (when SPS PDSCH is present) is received only for PCC: It is            possible to simultaneously transmit the CSI and A/N through            a PUCCH using TDD scheme 2.        -   Case #2) All cases other than case #1: It is possible to            drop the CSI, and transmit A/N over a PUCCH.    -   When there is a PUSCH transmission        -   It is possible to piggy back the CSI and A/N on the PUSCH to            transmit the CSI and A/N. In this case, no PUCCH is            transmitted.    -   In case of PUCCH+PUSCH ON and CSI+A/N OFF    -   When there is no PUSCH transmission        -   It is possible to drop the CSI, and transmit A/N through the            PUCCH.    -   When there is a PUSCH transmission        -   It is possible to piggy back the CSI on the PUSCH and            transmit A/N through the PUCCH.    -   In case of PUCCH+PUSCH ON and CSI+A/N ON    -   When there is no PUSCH transmission        -   Case in which application of TDD scheme 1 is considered        -   Case #1) one or more PDSCHs are received only for PCC: It is            possible to simultaneously transmit the CSI and A/N through            a PUCCH using TDD scheme 1.        -   Case #2) All cases other than case #1: It is possible to            drop the CSI, and transmit A/N through a PUCCH.        -   Case in which application of TDD scheme 2 is considered        -   Case #1) only one PDSCH (when SPS PDSCH is not present)            corresponding to a DAI initial value or only one SPS PDSCH            (when SPS PDSCH is present) is received only for PCC: It is            possible to simultaneously transmit the CSI and A/N through            a PUCCH using TDD scheme 2.        -   Case #2) All cases other than case #1: It is possible to            drop the CSI, and transmit A/N over the PUCCH.    -   When there is a PUSCH transmission        -   Case in which application of TDD scheme 1 is considered        -   Case #1) one or more PDSCHs are received only for PCC: It is            possible to simultaneously transmit the CSI and A/N through            a PUCCH using TDD scheme 1.        -   Case #2) All cases other than case #1: It is possible to            piggy back the CSI on the PUSCH and transmit A/N through the            PUCCH.        -   Case in which application of TDD scheme 2 is considered        -   Case #1) only one PDSCH (when SPS PDSCH is not present)            corresponding to a DAI initial value or only one SPS PDSCH            (when SPS PDSCH is present) is received only for PCC: It is            possible to simultaneously transmit the CSI and A/N through            a PUCCH using TDD scheme 2.        -   Case #2) All cases other than case #1: It is possible to            piggy back the CSI on the PUSCH transmit A/N over the PUCCH.

The above-described scheme may be combined with a scheme of embedding anSR in PUCCH format 2 for CSI transmission. Specifically, the scheme ofembedding ACK/NACK in PUCCH format 2 may be used when an SR transmissiontime and a CSI transmission time do not collide whereas the scheme ofembedding the SR in PUCCH format 2 may be used when the SR transmissiontime and CSI transmission time collide. Preferably, the scheme ofembedding the SR in PUCCH format 2 can be applied only when ACK/NACKinformation is not present at the corresponding time (time when SRtransmission and SCI transmission overlap).

Alternatively, when the CSI transmission time (that is, CSI subframe)and ACK/NACK transmission time collide, it is possible to joint-code CSIand ACK/NACK in the CSI subframe and then to transmit the joint-codedCSI and ACK/NACK through a payload of an arbitrary PUCCH resource (e.g.PUCCH format 2 (preferably, when ACK/NACK transmission is performedusing the ACK/NACK channel selection scheme) or through a payload ofPUCCH format 3 (preferably, when ACK/NACK transmission is performedusing the multi-bit ACK/NACK coding scheme)). In this case, the ACK/NACKis CW-bundled when the CSI and ACK/NACK are joint-coded in the CSIsubframe in order to prevent the PUCCH payload from abruptly increasingin the CSI subframe. Here, CW bundling is a scheme of transmitting 1-bitACK/NACK information bundled for a PDSCH of a CC configured with theMIMO transmission mode (e.g. when a plurality of CWs are transmittedthrough a PDSCH, ACK is signaled only when all the CWs of the PDSCHcorrespond to ACK, and NACK is signaled in other cases).

The above-mentioned scheme (i.e. joint coding in the CSI subframe) isapplicable both an FDD system and a TDD system. Application of CWbundling in the CSI subframe may be UE-specifically signaled throughL1/L2/RRC signaling.

FIG. 19 is a block diagram of a BS and a UE which can be applied to theembodiments of the present invention. When a relay is included in awireless communication system, communication is performed between the BSand the relay on a backhaul link and communication is establishedbetween the relay and the UE on an access link. Accordingly, the BS andthe UE shown in FIG. 22 can be replaced by a relay as necessary.

Referring to FIG. 19, a wireless communication system includes a BS 110and a UE 120. The BS 110 includes a processor 112, a memory 114, and anRF unit 116. The processor 112 may be configured so as to implement theprocedures and/or methods of the present invention. The memory 114 isconnected to the processor 112 and stores various pieces of informationrelated to operations of the processor 112. The RF unit 116 is connectedto the processor 112 and transmits and/or receives RF signals. The UE120 includes a processor 122, a memory 124, and an RF unit 126. Theprocessor 122 may be configured so as to implement the procedures and/ormethods of the present invention. The memory 124 is connected to theprocessor 122 and stores various pieces of information related tooperations of the processor 122. The RF unit 126 is connected to theprocessor 122 and transmits and/or receives RF signals. The BS 110and/or the UE 120 may have a single or multiple antennas.

The embodiments of the present invention described hereinbelow arecombinations of elements and features of the present invention. Theelements or features may be considered selective unless otherwisementioned. Each element or feature may be practiced without beingcombined with other elements or features. Further, an embodiment of thepresent invention may be constructed by combining parts of the elementsand/or features. Operation orders described in embodiments of thepresent invention may be rearranged. Some constructions of any oneembodiment may be included in another embodiment and may be replacedwith corresponding constructions of another embodiment. It is obvious tothose skilled in the art that claims that are not explicitly cited ineach other in the appended claims may be presented in combination as anembodiment of the present invention or included as a new claim by asubsequent amendment after the application is filed.

In the embodiments of the present invention, a description is made,centering on a data transmission and reception relationship between a BSand a UE. In some cases, a specific operation described as performed bythe BS may be performed by an upper node of the BS. Namely, it isapparent that, in a network comprised of a plurality of network nodesincluding a BS, various operations performed for communication with anMS may be performed by the BS, or network nodes other than the BS. Theterm ‘eNB’ may be replaced with the term ‘fixed station’, ‘Node B’,‘Base Station (BS)’, ‘access point’, etc. The term ‘UE’ may be replacedwith the term ‘Mobile Station (MS)’, ‘Mobile Subscriber Station (MSS)’,‘mobile terminal’, etc.

The embodiments of the present invention may be achieved by variousmeans, for example, hardware, firmware, software, or a combinationthereof. In a hardware configuration, the methods according to theembodiments of the present invention may be achieved by one or moreApplication Specific Integrated Circuits (ASICs), Digital SignalProcessors (DSPs), Digital Signal Processing Devices (DSPDs),Programmable Logic Devices (PLDs), Field Programmable Gate Arrays(FPGAs), processors, controllers, microcontrollers, microprocessors,etc.

In a firmware or software configuration, the embodiments of the presentinvention may be implemented in the form of a module, a procedure, afunction, etc. For example, software code may be stored in a memory unitand executed by a processor. The memory unit is located at the interioror exterior of the processor and may transmit and receive data to andfrom the processor via various known means.

Those skilled in the art will appreciate that the present invention maybe carried out in other specific ways than those set forth hereinwithout departing from the spirit and essential characteristics of thepresent invention. The above embodiments are therefore to be construedin all aspects as illustrative and not restrictive. The scope of theinvention should be determined by the appended claims and their legalequivalents, not by the above description, and all changes coming withinthe meaning and equivalency range of the appended claims are intended tobe embraced therein.

INDUSTRIAL APPLICABILITY

The present invention is applicable to wireless communicationapparatuses such as a UE, a relay, a BS, etc.

1. A method of transmitting uplink control information at acommunication apparatus in a Time Division Duplex (TDD) wirelesscommunication system, the method comprising: receiving at least one ofone or more Physical Downlink Control CHannels (PDCCHs) and one or morePhysical Downlink Shared CHannels (PDCCHs); and generating receptionresponse information about the at least one of the one or more PDCCHsand the one or more PDCCHs, wherein when a transmission time of thereception response information and a transmission time of channel statusinformation are collided, if a certain condition is satisfied, thereception response information and the channel status information aretransmitted together using a first Physical Uplink Control CHannel(PUCCH) format, wherein when the transmission time of the receptionresponse information and the transmission time of the channel statusinformation are collided, if the certain condition is not satisfied, thereception response information is transmitted using a second PUCCHformat and the channel status information is dropped, wherein thecertain condition includes at least one of the following conditions (1)to (3): (1) a single PDSCH transmission only on a Primary Cell (PCell)indicated by detection of a PDCCH having a Downlink Assignment Index(DAI) initial value is present; (2) a single PDCCH transmission only onthe PCell that has the DAI initial value and indicates a Semi-PersistentScheduling (SPS) release is present; and (3) a single PDSCH transmissiononly on the PCell where there is not a corresponding PDCCH is present.2. The method of claim 1, wherein if the certain condition is notsatisfied, resource for the second PUCCH format is indicated by a valueof Transmit Power Control (TPC) field of one or more Secondary Cell(SCell) PDCCH and/or one or more PCell PDCCH not correspond to the DAIinitial value.
 3. The method of claim 1, wherein the at least one of oneor more Physical Downlink Control CHannels (PDSCHs) and one or morePhysical Downlink Shared CHannels (PDSCHs) is received in a subframe n−k(kεK), the reception response information is transmitted in a subframen, and K is given by the below table in accordance with UL-DLconfiguration. UL-DL Configu- Subframe n ration 0 1 2 3 4 5 6 7 8 9 0 —— 6 — 4 — — 6 — 4 1 — — 7, 6 4 — — — 7, 6 4 — 2 — — 8, 7, 4, 6 — — — —8, 7, — — 4, 6 3 — — 7, 6, 11 6, 5 5, 4 — — — — — 4 — — 12, 8, 7, 6, 5,— — — — — — 11 4, 7 5 — — 13, 12, 9, — — — — — — — 8, 7, 5, 4, 11, 6 6 —— 7 7 5 — — 7 7 —


4. The method of claim 1, wherein the DAI initial value is
 1. 5. Themethod of claim 1, wherein the first PUCCH format is a PUCCH format 2,2a or 2b.
 6. The method of claim 1, wherein the second PUCCH format is aPUCCH format
 3. 7. A communication apparatus configured to transmituplink control information in a Time Division Duplex (TDD) wirelesscommunication system, the communication apparatus comprising: a RadioFrequency (RF) unit; and a processor configured to receive at least oneof one or more Physical Downlink Control CHannels (PDCCHs) and one ormore Physical Downlink Shared CHannels (PDSCHs), and to generatereception response information about the at least one of the one or morePDCCHs and the one or more PDSCHs, wherein when a transmission time ofthe reception response information and a transmission time of channelstatus information are collided, if a certain condition is satisfied,the reception response information and the channel status informationare transmitted together using a first Physical Uplink Control CHannel(PUCCH) format, wherein when the transmission time of the receptionresponse information and the transmission time of the channel statusinformation are collided, if the certain condition is not satisfied, thereception response information is transmitted using a second PUCCHformat and the channel status information is dropped, wherein thecertain condition includes at least one of the following conditions (1)to (3): (1) a single PDSCH transmission only on a Primary Cell (PCell)indicated by detection of a PDCCH having a Downlink Assignment Index(DAI) initial value is present; (2) a single PDCCH transmission only onthe PCell that has the DAI initial value and indicates a Semi-PersistentScheduling (SPS) release is present; and (3) a single PDSCH transmissiononly on the PCell where there is not a corresponding PDCCH is present.8. The communication apparatus of claim 7, wherein if the certaincondition is not satisfied, resource for the second PUCCH format isindicated by a value of Transmit Power Control (TPC) field of one ormore Secondary Cell (SCell) PDCCH and/or one or more PCell PDCCH notcorresponding to the DAI initial value.
 9. The communication apparatusof claim 7, wherein the at least one of one or more Physical DownlinkControl CHannels (PDCCHs) and one or more Physical Downlink SharedCHannels (PDSCHs) is received in a subframe n−k (kεK), the receptionresponse information is transmitted in a subframe n, and K is given bythe below table in accordance with UL-DL configuration. UL-DL Configu-Subframe n ration 0 1 2 3 4 5 6 7 8 9 0 — — 6 — 4 — — 6 — 4 1 — — 7, 6 4— — — 7, 6 4 — 2 — — 8, 7, 4, 6 — — — — 8, 7, — — 4, 6 3 — — 7, 6, 11 6,5 5, 4 — — — — — 4 — — 12, 8, 7, 6, 5, — — — — — — 11 4, 7 5 — — 13, 12,9, — — — — — — — 8, 7, 5, 4, 11, 6 6 — — 7 7 5 — — 7 7 —


10. The communication apparatus of claim 7, wherein the DAI initialvalue is
 1. 11. The communication apparatus of claim 7, wherein thefirst PUCCH format is a PUCCH format 2, 2a or 2b.
 12. The communicationapparatus of claim 7, wherein the second PUCCH format is a PUCCH format3.